A wellbore of a well is typically completed by cementing a casing string in at least the upper portion of the wellbore. The wellhead of the well typically includes a casing head or casing bowl engaging or otherwise mounted to the casing string at the surface. The remainder of the wellhead, which may comprise any number of further elements or apparatuses, is then mounted to or upon the casing bowl. Where the wellhead does not include a casing bowl, the upper end of the casing string itself may be used to support the wellhead.
Further, the wellhead typically includes a tubing hanger, or other support mechanism, connected to or engaging an upper end of a tubing string contained within the wellbore. The tubing hanger thus acts to support or suspend the tubing string within the wellbore at the surface of the well. As well, a reciprocating rod string or a rotating rod string, supported by the wellhead, is typically run through the tubing string for production of the well.
In particular, many wells today utilize progressive cavity pumps to lift fluids from the bottom of the production well to the surface. The progressive cavity pump system includes a downhole pump and a sucker rod string supported by the wellhead in the wellbore. Specifically, the downhole pump is driven by a drive assembly or top drive forming part of the wellhead, which drive assembly drives the downhole pump by rotation of the rod string. Production fluids are transported to the surface through the tubing string.
The wellhead may also include a tubing rotator. Tubing rotators are used in the industry to suspend and rotate the tubing string within the wellbore. By rotating the tubing string, typical wear occurring within the internal surface of the tubing string by the reciprocating or rotating rod string is distributed over the entire internal surface of the tubing string. As a result, the tubing rotator may prolong the life of the tubing string. Further, the constant movement of the tubing string relative to the rod string may inhibit or reduce the buildup of wax and other materials within the tubing string.
When a tubing rotator is in use in the wellhead, the tubing hanger is typically comprised of a swivel tubing hanger or swivel dognut assembly. The swivel tubing hanger is comprised of a rotatable mandrel, which is connected to and suspends the tubing string within the wellbore, and a drive system for rotating the mandrel which results in the rotation of the tubing string. The drive system is conventionally comprised of a system of gears which engages the mandrel either directly or indirectly to cause it to rotate. More particularly, the swivel tubing hanger includes a driven gear which is engaged with a drive gear associated with a rotatable member. The driven gear and the drive gear comprise the drive system of the tubing rotator which causes the tubing string connected to the swivel tubing hanger to be rotated within the wellbore.
In order to provide even distribution of the wear on the tubing string, the tubing string is preferably turned automatically on a continuous basis. As well, it may be preferred that other apparatuses associated with the wellhead similarly be operated on an automatic basis. Several mechanisms or means for operating tubing rotators on a continuous basis are known.
For instance, tubing rotators are typically driven by an alternating current or direct current electric motor or by a hydraulic motor depending upon the energy source available at the well site. Where the progressive cavity pump drive assembly is driven by an alternating current electric motor, the tubing rotator is usually driven by a separate alternating current electric motor. Where alternating current is not available, the progressive cavity pump drive assembly may be driven by a hydraulic motor that is powered by hydraulic fluid received from a pump driven by an internal combustion engine. In this case, the tubing rotator can also be driven by a hydraulic motor utilizing hydraulic fluid from the same source or by a 12 volt direct current electric motor connected to the battery of the internal combustion engine. One example is shown in U.S. Pat. No. 2,630,181 issued Mar. 3, 1953 to Solum, which describes an apparatus for continuously rotating the tubing string which is operated by hydraulic pressure.
However, the means for operating the tubing rotator are preferably driven by, and combined with, the producing action of the wellhead, as shown in U.S. Pat. No. 2,471,198 issued May 24, 1949 to Cormany, U.S. Pat. No. 2,595,434 issued May 6, 1952 to Williams, U.S. Pat. No. 5,139,090 issued Aug. 18, 1992 to Land and U.S. Pat. No. 2,693,238 issued Nov. 2, 1954 to Baker. These patents all provide for a tubing rotator which is connected to a wellhead having a reciprocating rod string attached to a walking beam. The tubing rotator is continuously driven by the reciprocating action or movement of the walking beam. However, the operating means described in these patents may not always be useful given that many wellheads today use a rotating rod string for production of the well rather than a reciprocating rod string and walking beam structure.
U.S. Pat. No. 5,427,178 issued Jun. 27, 1995 to Bland continuously drives the tubing rotator by the action of a rotating rod string. More particularly, the Bland patent describes an adaptor for connection to the rotating rod string for automatically driving a tubing rotator or other apparatus. The adaptor operatively connects the rotating rod string to the means for rotating the tubing string such that rotation of the rod string operates the rotating means in order to rotate the tubing string within the wellbore.
The adaptor of Bland is comprised of: a sleeve that is mountable about the rotating rod string such that rotation of the rod rotates the sleeve; a shaft having an end engaged with the sleeve such that rotation of the sleeve rotates the shaft; and an adaptor housing, mounted about the sleeve, for supporting the end of the shaft such that the sleeve is rotatable within the adaptor housing. More particularly, the end of the shaft engages an outer surface of the sleeve in a manner such that the longitudinal axis of the shaft intersects the longitudinal axis of the sleeve. In the preferred embodiment, the axis of the shaft is perpendicular to the axis of the sleeve. Further, the end of the shaft comprises a pinion which engages a crown gear on the outer surface of the sleeve. Therefore, the housing is mounted about the sleeve in order to support the end of the shaft (being the pinion) in proper engagement with the crown gear of the sleeve.
The adaptor of the Bland patent, described for operatively connecting the rotating rod string to the tubing rotator or other apparatus, may not be desirable or economically feasible for some applications given the specific structure of the adaptor as described above.
Therefore, there is a need in the industry for an improved device for connection to a wellhead for coupling a drive assembly for a downhole pump with a tubing rotator or other apparatus associated with the wellhead, the apparatus having a rotatable member for driving the apparatus.